1. Field of the Invention
The present invention relates to a recording tape cartridge which rotatably accommodates a single reel onto which a recording tape, such as a magnetic tape or the like, which is used as a recording/play back medium of a computer or the like, is wound.
2. Description of the Related Art
Conventionally, magnetic tape cartridges have been known in which a magnetic tape, which is used as a data recording/playback medium of a computer or the like, is wound on a single reel and the reel is accommodated within a case. A leader member, such as a leader block or a leader pin, for example, is provided at a distal end of the magnetic tape. A drawing-out means, which is provided at a drive device, pulls out the leader member from the magnetic tape cartridge, so that the magnetic tap fixed to the leader member is wound onto a take-up reel of the drive device.
Writing and reading of information on the magnetic tape can be carried out by synchronously rotating the magnetic tape cartridge and the take-up reel of the drive device. The reel of the magnetic tape cartridge is structured such that a cylindrical hub and a bottom flange portion radially projecting from a periphery of a bottom end of the hub are integrally formed, and a top flange portion having the same shape as the bottom flange portion is joined to a top end of the hub. Then, the magnetic tape is wound around a peripheral surface of the hub.
As shown in FIG. 4, a reel gear 108 is carved in an annular shape at a center of a bottom surface of a reel 104 (or a bottom flange portion 106), and the reel 104 is exposed from an opening 102 formed in a bottom surface of a case 100. Due to a drive gear 110, which is provided on a rotating shaft of a drive device, meshing with the reel gear 108, the reel 104 is driven to rotate. In other words, through the substantially serrated reel gear 108 and the substantially serrated drive gear 110 which mesh with one another, a driving force for rotation is transmitted from the drive device to the reel 104 such that the reel 104 is driven to rotate.
However, when the drive gear 110 is rotated relative to the drive gear 110, for example, in the direction indicated by arrow R in FIG. 4B, the drive gear 110 is likely to move the reel gear 108 upward, thereby causing small misalignments or clearances S to be formed between the meshing portions of the drive gear and the reel gear. Due to such misalignments or clearances S, so-called “surge” is generated in which the bottom flange portion 106 wobbles up and down. Therefore, there is a risk that this surge may have an undesirable effects on the feeding and rewinding of the magnetic tape T. Additionally, the meshing portions define a heightwise direction central position thereof, that is indicated by an imaginary line K in FIG. 4B, when seen from the side, as a reference portion (reference surface) in the heightwise direction of the reel 104 with respect to the drive device. Thus, if surge due to the misalignments or clearances S occurs in the meshing portions of the above two members, it may become difficult to obtain accurate positioning due to the fluctuation of the reference portion position.